java empty catch block

gudii9
gudii9 used Ask the Experts™
on
Avoid Empty Catch Blocks
It’s a very bad habit to leave catch blocks empty, as when the exception is caught by the empty catch block, the program fails in silence, which makes debugging harder. Consider the following program which calculates sum of two numbers from command-line arguments:
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public class Sum {
    public static void main(String[] args) {
        int a = 0;
        int b = 0;
 
        try {
            a = Integer.parseInt(args[0]);
            b = Integer.parseInt(args[1]);
 
        } catch (NumberFormatException ex) {
        }
 
        int sum = a + b;
 
        System.out.println("Sum = " + sum);
    }
}
Note that the catch block is empty. If we run this program by the following command line:
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java Sum 123 456y
It will fail silently:
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Sum = 123

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when i tried above example i am getting different error as below istead of getting 123


public class Sum {
    public static void main(String[] args) {
        int a = 0;
        int b = 0;
 
        try {
            a = Integer.parseInt(args[0]);
            b = Integer.parseInt(args[1]);
 
        } catch (NumberFormatException ex) {
        }
 
        int sum = a + b;
 
        System.out.println("Sum = " + sum);
    }
}

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Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0
      at Sum.main(Sum.java:7)

https://www.codejava.net/coding/10-java-core-best-practices-every-java-programmer-should-know

even below good catch block example also gives same error
public class SumFixed {
    public static void main(String[] args) {
        int a = 0;
        int b = 0;
 
        try {
            a = Integer.parseInt(args[0]);
            b = Integer.parseInt(args[1]);
 
        } catch (NumberFormatException ex) {
            System.out.println("One of the arguments are not number." +
                               "Program exits.");
            return;
        }
 
        int sum = a + b;
 
        System.out.println("Sum = " + sum);
    }
}

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Senior Director of Technologyy
Commented:
You are assuming there is an argument passed into your class.  The array String[] args does not have anything in it, so when you try to do Integer.parseInt(args[0]); you get the ArrayIndexOutOfBoundsException.  A good way to get rid of this is to check the length of the array passed in before trying to grab and element from a specific spot.

Author

Commented:
when i pass argument while Run As Java application and arguments tab in eclipse i do see this behavior correctly between eating exception catch message and keeping catch message

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